In order to perform well in the game of golf, a golfer needs to be able to execute a variety of different golf shots; with each one of them focusing on a different aspect of the golf game. For example, in order to execute a good chip and or pitch shot, a golfer needs to be able to control the trajectory, distance, and spin of a golf ball for the golf ball to come to rest at a location that is as close to the pin as possible; or more preferably in the hole. In another example, in order to execute a good iron shot, a golfer needs to control the distance and dispersion of the golf shot to ensure that it lands on the green; sacrificing some accuracy in an attempt to achieve distance gains. Finally, in another example, in order to execute a good driver shot, a golfer needs to maximize the distance of the golf shot while maintaining a relatively straight flight path. Based on the above, it can be seen that as the clubs get longer and longer, less and less emphasis is placed on accuracy, and more and more emphasis is placed on distance.
With respect to drive type shots, golf club designers have always attempted to design wood type golf clubs that increases the overall distance of the golf shot while maintaining a relatively straight flight path. U.S. Pat. No. 6,932,716 shows one attempt of increasing the overall distance of a driver type golf club by increasing the coefficient of restitution of the driver type golf club head. More specifically U.S. Pat. No. 6,932,716 attempts to achieve this by creating a golf club head having a matrix layer composed of an interconnected reinforcement structure and a polymer material, wherein the matrix layer provides the golf club head with a greater coefficient of restitution during impact with a golf ball. U.S. Pat. No. 6,719,644 provides another example of increasing the distance of a driver type golf club head by using shallow markings that prevent stress fracture, resulting in a thinner face that provides improved coefficient of restitution.
In order to help golfers maintain a relative straight flight path in a drive type golf shot, golf club designers have attempted to create larger club heads that results in an increase in the moment of inertia of these oversized club heads; as an increase in the moment of inertia prevents the club head from undesirable twisting at impact that could send a golf shot off the intended path. U.S. Pat. No. 7,413,520 provides one example of increasing the overall size of the golf club head to help a golfer hit a ball straighter. More specifically, U.S. Pat. No. 7,413,520 discloses a golf club head having a volume ranging from 450 cubic centimeters to 475 cubic centimeters, a mass ranging from 180 grams to 225 grams, and a front to back length ranging from 4.0 inches to 5.0 inches. Moreover, U.S. Pat. No. 7,413,520 also illustrates one of the incidental effects is an increase in the moment of inertia, Iyy, about the center of gravity of the golf club head achieving numbers greater than 4000 grams-centimeters squared.
Although increasing the coefficient of restitution and the moment of inertia of a golf club head both help a golfer hit a golf ball longer and straighter, they are not the be all and end all in achieving longer and straighter drives. In fact, the size of the sweet spot is another one of those factors that can make a significant difference, but is often overlooked. U.S. Pat. No. 5,839,975 identifies the importance of the sweet spot by creating a golf club head a rib structure within the internal cavity of the golf club head to reinforce the club head to prevent collapse or other distortion while providing a relatively large sweet spot. Although U.S. Pat. No. 5,839,975 provides one of the earlier attempts of identifying and increasing the size of the sweet spot of a golf club head, it does so by adding additional material to the internal cavity of the golf club head, which can often be undesirable. In order to achieve the same goal without adding weights, a golf club designer could potentially use different materials to form the striking face.
U.S. Pat. No. 3,975,023 shows an early attempt at the usage of multiple different materials at or near the striking face portion of the golf club head, however, it does so in an attempt to increase the overall flying distance of a golf ball, and makes no mention of increasing the size of the sweet spot. U.S. Pat. No. 3,795,023 discloses a golf club that fixes the striking face of the club head with a ceramic face plate made of a sintered body of metallic oxides such as alumina ceramics, mullite ceramics, etc.
U.S. Pat. No. 7,874,938 provides a more modern attempt to use multiple different materials by using composite articles on the face plate. More specifically, U.S. Pat. No. 7,874,938 discloses a golf club head having a composite face plate, wherein the composite face plate can be made by first forming an oversized lay-up of multiple prepreg plies having a central portion and a sacrificial portion surrounding the central portion. The lay-up is at least partially cured in a mold under elevated pressure and heat, then the lay-up is then removed from the mold and the sacrificial portion is removed from the central portion to form a composite part that is substantially free of defects. However, similar to above, U.S. Pat. No. 7,874,938 makes no mention of the ability to increase the sweet spot of a golf club head.
Hence, it can be seen from above, despite all the development in recognizing the importance of increasing the size of the sweet spot, the current art is incapable of achieving improvements in sweet spot size without adding undesirable weight. On the other hand, the only attempts of using multiple materials at the striking face without increasing weight fails to incorporate a design that could increase the size of the sweet spot. Hence, there is a need in the art for a golf club head that is capable of utilizing multiple materials in a way that can increase the size of the sweet spot of a golf club head.